Pain under the left side of the chest when breathing should first clarify the etiology of pain under the left side of the chest when breathing. Common breathing-related chest pain is mainly seen in pleuritic chest pain, and chest pain caused by chest wall diseases. When chest pain occurs, chest X-ray or CT examination, as well as electrocardiogram, blood D-dimer and other corresponding examinations should be improved immediately. If it is caused by pleurisy, anti-inflammatory or anti-tuberculosis treatment should be used according to the situation. In case of pneumothorax, closed drainage of the chest cavity is feasible. Those caused by intercostal neuralgia or intercostal chondritis, muscle injury, etc. can be treated with symptomatic treatment such as physiotherapy, nerve nutrition and local closure while relieving pain. When chest pain related to respiration occurs, we should also try to avoid coughing, excessive activity and exercise that induce an increase in the amplitude of respiratory movement and aggravate chest pain. Therefore, through the above symptomatic treatment, chest pain can be relieved significantly.